(217fb) Biodegradable Film From Polylactic Acid/Thermoplastic Starch Blends

Polylactic acid (PLA) is a thermoplastic aliphatic polyester derived from the polymerization of lactic acid, which is a product of bacterial fermentation of carbohydrates.  PLA can be processed into fibers, films, sheets and 3D articles using the existing polymer processing equipment and techniques, such as fiber drawing, film blowing, extrusion, and injection molding.  Although PLA is suitable for biodegradable packaging, such as bottles, food containers, bags and wrappers due to its clarity; the rigidity, brittleness and expensiveness of PLA compared with conventional plastics limit its utilization, particularly in the form of film.  Blending PLA with ductile polymers is probably the most convenient for overcoming its brittleness and reducing its cost.  Thermoplastic starch (TPS) is an attractive material to be blended with PLA since it is made from starch, which is naturally abundant, cheap, renewable, non-toxic, biodegradable and compostable.  Therefore, the objective of the present work is to develop PLA/TPS blends for blown film extrusion industry.  PLA and TPS were melt blended in a twin-screw extruder using a weight ratio of PLA:TPS of 60:40.  The PLA/TPS blends were then converted to film using a blown film extruder.  The properties of the blend films were compared with those of three commodity plastic films, i.e. PLA, Mater-Bi and LDPE.  The thickness of the PLA/TPS blend films was about 20-28 mm, which was in the same range as those of commodity plastic films.  The blends showed higher melt flow ability than PLA and LDPE, but lower than Mater-Bi.  Similar to PLA film, the blend films were strong and stiff, but exhibited low extensibility.  These characteristics were significantly different from the ones of Mater Bi and LDPE films.  The blend films possessed the greatest oxygen barrier property; however they had the lowest water vapor barrier property.  As compared to the PLA film, the PLA/TPS blend films exhibited improved extensibility, greater biodegradability, better oxygen barrier property and less loudness when handling.  The resulting PLA/TPS films also showed feasibility to be used as packaging plastic bag for fresh produces, with competitive price to the plastic bags made from commodity bioplastic films.